Machine Type Communication (MTC) User Equipment (UE), also known as a Machine to Machine (M2M) user communication device, is a major application form of the Internet of Things at present, and have been applied massively mainly because of low power consumption and low cost. M2M devices on the market are mainly based on a Global System of Mobile communication (GSM) system. In recent years, more and more mobile operators choose Long Term Evolution (LTE)/LTE-Advanced (LTE-A) as a direction for evolution of future broadband wireless communications systems since the spectral efficiency of LTE and LTE-A improves, and various types of M2M data services based on LTE/LTE-A will also become more attractive. An M2M service may be truly transferred from a GSM system to an LTE system only when an LTE M2M device is manufactured with a lower cost than that of an MTC terminal of the GSM system.
At present, major alternatives for reducing the cost of an MTC UE include: reduction of the number of receiving antennae of the terminal, reduction of baseband processing bandwidths of the terminal, reduction of a peak rate supported by the terminal, and application of a half-duplex mode and so on. However, the reduction of the cost means performance reduction. Since demands for cell coverage of an LTE/LTE-A system cannot be reduced, it is necessary to take some measures so as to satisfy demands for the coverage performance of an existing LTE terminal when the MTC terminal configured at low cost is applied. Besides, the MTC terminal may locate in a basement, a corner of a wall and so on, and may be in a worse scenario than a common LTE UE. It is necessary to improve the performance of some MTC UEs in order to compensate the reduction in coverage due to penetration loss, thus it is necessary to enhance uplink and downlink coverage of some MTC UEs in such a scenario, while the first consideration is how to guarantee the access quality of a user. It is necessary to design an enhanced random access channel (referred to a Physical Random Access Channel (PRACH)) of the LTE/LTE-A system so as to ensure that the MTC UE is able to access the system normally.
An evolved Node B (eNB) in the LTE/LTE-A system may allocate a dedicated random access sequence (also called a PRACH preamble) to a UE in a non-contention random access flow. The UE may send the PRACH preamble on a Physical Resource Block (PRB) allocated by the eNB to the UE, and may improve the transmission power of the PRACH preamble successively until the UE is able to detect, from a Random Access Response (RAR) sent by the eNB, RAR information sent to the UE. The UE receives and decodes the RAR information to obtain uplink time synchronization and an uplink resource, and sends an Msg3 message on the uplink resource so as to complete the random access flow based on non-contention. The Msg3 message is the first message transmitted on a Physical Uplink Shared Channel (PUSCH) by using a Hybrid Automatic Repeat Request (HARQ) mechanism based on uplink scheduling.
Access of an MTC UE that requires Coverage Improvement (CI) to a system is not necessarily guaranteed even if a PRACH preamble is transmitted at full power, thus the power of the MTC UE with CI can be hardly improved in the non-contention random access flow. Therefore, it is necessary to provide a random access solution based on the CI MTC UE in such a scenario so as to ensure that the CI MTC UE can access the system normally.